The present invention relates generally to new and novel improvements in a variable height print table arrangement for a screen printing apparatus. More particularly, the present invention relates to a variable height print table arrangement for a screen printing apparatus which is capable of lowering the print tables in a screen printing apparatus a predetermined variable distance to facilitate the screen printing process.
The application of text, logos and other indicia onto apparel, such as tee shirts, sweatshirts and jackets as well as other textile substrates, has become very popular. Fanciful indicia, such as logos, slogans, school names, sports team names and sayings, are commonplace. As a result, screen printing has become very prevalent and large commercial screen printing operations are common today.
Indicia can be printed onto apparel and other textile substrates in one or more colors. Typically, a screen printing apparatus has at least one station for each color to be printed onto the apparel and other textile substrates. For example, a design utilizing two (2) colors will typically have at least two (2) printing stations, one for each color. Similarly, a design utilizing eight (8) colors will typically have at least eight (8) printing stations, one for each color. Each printing station generally includes a printing head which supports a single screen, the ink of the color to be applied at that printing station and a mechanism for applying the ink of the color to be applied to the apparel or other textile substrates. Each color is generally carried by a single screen and the apparel or other textile substrates travel from one printing station to the next printing station by a number of methods, including a chain or rigid arm. The apparel or other textile substrates are generally carried from one printing station to the next printing station by a support pallet or table. In addition to printing stations, there may also be one or more curing stations provided to heat and set the inks placed on the apparel or other textile substrates.
In a turret or carrousel type screen printing apparatus, a center section generally includes a plurality of outwardly extending spider arms. Generally, two (2) levels of outwardly extending spider arms are provided, a stationary upper level which carries the printing heads and screens or the curing assemblies and a rotating lower level which carries the support pallets or tables upon which the apparel or other textile substrates are placed for printing. The stationary upper level outwardly extending spider arms are generally referred to as xe2x80x9cstationsxe2x80x9d and the rotatable lower level outwardly extending spider arms generally rotate from xe2x80x9cstationxe2x80x9d to xe2x80x9cstation.xe2x80x9d In particular, the rotatable lower level outwardly extending spider arms typically rotate from one xe2x80x9cstationxe2x80x9d to the next xe2x80x9cstationxe2x80x9d where the printing operations and/or curing operations are carried out.
Prior to rotation of the lower level outwardly extending spider arms to allow the support pallets or tables to move from one xe2x80x9cstationxe2x80x9d to the next xe2x80x9cstation,xe2x80x9d the support pallets or tables are typically lowered to avoid interference with the printing heads and curing equipment in the stationary upper level outwardly extending spider arms. This lowering of the support pallets or tables has typically been accomplished by one or more air cylinders which lower each support pallet or table a fixed distance or xe2x80x9cstrokexe2x80x9d which is not readily adjustable.
However, there are situations where it is desirable to carry out two (2) or more printing and/or curing operations at a single station, for example, to double coat an ink of a certain color. In such situations, the support pallets or tables are lowered the fixed distance or xe2x80x9cstrokexe2x80x9d by the one or more air cylinders and are again raised at the same station without rotation of the lower level of outwardly extending spider arms. In such situations, the lowering and raising of the support pallets or tables a fixed distance or xe2x80x9cstrokexe2x80x9d by the one or more air cylinders takes longer than desirable and has a negative impact on the overall efficiency and cycle time of the screen printing operation.
In addition, there are situations where it is desirable to adjust the top and/or the bottom position of the support pallets or tables to accommodate, for example, inks having different characteristics, such as different densities and compositions, apparel or other textile substrates having different characteristics, such as different absorbencies, and printing screens having different characteristics, such as the size and flexibility or rigidity of the printing screens. With known prior art support pallets using one or more air cylinders, the top and bottom positions or xe2x80x9cstopsxe2x80x9d of the fixed distance or xe2x80x9cstrokexe2x80x9d are generally fixed and are not readily adjustable.
Accordingly, an object of the present invention is the provision of a variable height print table arrangement for a screen printing apparatus which allows the support pallets or tables to be raised and lowered a predetermined variable distance.
Another object of the present invention is the provision of a variable height print table arrangement for a screen printing apparatus which allows the support pallets or tables to be raised and/or lowered to specific predetermined adjustable positions or xe2x80x9cstopsxe2x80x9d in relation to the printing, curing and other processing stations.
Yet another object of the present invention is the provision of a variable height print table arrangement for a screen printing apparatus which includes a counterbalance arrangement which reduces the effective weight of the rotating lower level outwardly extending spider arms and permits the use of a smaller motor having less weight and size and which is less expensive to operate than motors used in many known prior art screen printing apparatus or, alternatively, provides faster movement if a motor of the same size is used.
Yet another object of the present invention is the provision of a variable height print table arrangement for a screen printing apparatus in which the rotating lower level outwardly extending spider arms are capable of being selectively indexed to rotate to the next station or to remain at the same station for one or more subsequent operation(s).
These and other objects of the present invention are attained by a variable height print table arrangement for a screen printing apparatus which includes a plurality of rotatable lower level outwardly extending spider arms which support corresponding support pallets or tables on which apparel or other textile substrates to be screen printed are placed. The rotatable lower level outwardly extending spider arms are lowered and raised using a mechanical drive, such as a an electrical servomotor or stepper motor, which is capable of lowering and raising the rotatable lower level outwardly extending spider arms a predetermined variable distance. The variable height print table arrangement for a screen printing apparatus also includes a counterbalance arrangement, preferably using a compression spring, which reduces the effective weight of the rotatable lower level outwardly extending spider arms and allows a smaller mechanical drive to be used. This results in a screen printing apparatus which is smaller, has less weight and is less expensive to operate than many known prior art screen printing apparatus.
Other advantages and novel features of the present invention will become apparent in the following detailed description of the invention when considered in conjunction with the accompanying drawings.